Helen Goldsworthy

Interior wide beam connections subjected to lateral earthquake loading

Abstract The use of wide beam–column systems has become increasingly popular in low to moderate seismic regions, despite very little information being available on their performance under seismic action. Therefore, this investigation was conducted to determine the behavior and likely failure mode of wide beam connections when subjected to earthquake loading. In this investigation, two interior reinforced concrete wide beam subassemblages and one post-tensioned concrete wide beam subassemblage were tested under quasi-static cyclic loading up to a drift ratio of 3.5%. It was found that the wide beam connection is likely to experience severe torsion cracking in the beam portions located at the sides of the column when subjected to severe earthquake loading. A special detailing strategy was developed to inhibit the torsion cracking and was found to be effective in the subsequent tests. The experimental behavior of the subassemblages is reported in this paper.

Reinforced Concrete Interior Wide-Band Beam-Column Connections Subjected to Lateral Earthquake Loading

This paper presents experimental results from quasistatic cyclic lateral load tests on 2 half-scale reinforced concrete interior wide-band beam-column subassemblages. The 1st connection is detailed without any special provision for seismicity, and the 2nd connection is similarly detailed with a few modifications that are shown to improve the performance of the connection. The 2nd connection includes a unique detailing strategy involving the debonding of reinforcing bars to prevent the formation of undesirable torsion and shear cracks. This connection is shown to perform very well up to the maximum applied 4% nominal drift; thus, a recommendation is made that limits on beam width in regions of high seismicity could be removed from current design codes if the unique detailing strategy is employed.

Displacement-based assessment of non ductile exterior wide band beam-column connections

Results from testing two half-scale exterior wide band beam-column sub-assemblages under cycles of lateral displacement are presented in this article. The first subassemblage represents the current level of detailing adopted in low to moderate seismic regions, such as Australia, for connections where seismic provisions are not normally a consideration in design. Minor (inexpensive) detailing changes in the reinforcement distribution and anchorage were introduced to the second test specimen. These changes significantly improved the connection performance in terms of increased displacement capacity and a reduction in strength deterioration. Using a displacement-based assessment approach to assess primary moment-resisting band beam frames of up to eight stories, it was found that the current level of detailing is adequate for the drift demands resulting from the expected Australian seismicity for a 500-year return period. However, for the displacement demands corresponding to a 2500-year return period, the frames sited on very soft soils and frames over four stories sited on intermediate soils would require improved detailing such as that used in the second sub-assemblage. A strength hierarchy of strong column-weak beam was assumed in this assessment.

Tensile Behavior of Groups of Anchored Blind Bolts within Concrete-Filled Steel Square Hollow Sections

AbstractIn this paper, the tensile behavior of groups of Ajax anchored blind bolts used within concrete-filled steel square hollow sections is investigated. Using Ajax anchored blind bolts moment-resisting bolted connections to concrete-filled steel hollow section columns will be possible. Extensive experimental and numerical studies were undertaken. Bolt sizes and section sizes suitable for medium-rise commercial buildings were used. It was concluded that the groups of Ajax anchored blind bolts can reach the ultimate capacity of equivalent groups of standard structural bolts. The location of an Ajax anchored blind bolt relative to the section side walls has a significant influence on its behavior. For bolts located close to the side walls of a section, concrete struts developed and transferred the loads to the corner of the sections. Bolt diameter, concrete grade, and strut angle were found to be the most influential factors in the stiffness of an Ajax anchored blind bolt. A simple theoretical model, bas...

Plastic Hinge Length for Lightly Reinforced Rectangular Concrete Walls

ABSTRACT This research investigates the plastic hinge length in lightly reinforced rectangular walls typically found in regions of low-to-moderate seismicity. Poor performance has been exhibited by lightly reinforced concrete walls in past earthquake events. A series of finite element analyses have been carried out which demonstrate that if the longitudinal reinforcement ratio in the wall is below a certain threshold value, there will not be sufficient reinforcement to cause secondary cracking, and instead fracture of the longitudinal reinforcement at a single crack could occur. A plastic hinge length equation has been derived based on the results from the numerical simulations.

Group Behavior of Double-Headed Anchored Blind Bolts within Concrete-Filled Circular Hollow Sections under Cyclic Loading

AbstractSeven full-scale curved T-stubs connected to concrete-filled circular hollow sections (CFCHSs) using groups of double-headed anchored blind bolts (DHABBs) have been cyclically tested in thi...

The Influence of Key Design Parameters on the Cyclic Axial Behavior of Innovative Replaceable Buckling Restrained Fuses (RBRFs)

ABSTRACT behaviorA detailed parametric study was conducted to determine the influence of the key parameters affecting the cyclic axial of replaceable buckling restrained fuses (RBRFs). These RBRFs are developed for use in damage-resistant moment-resisting connections. A sufficiently low ratio of maximum compressive force to maximum tensile force () at the RBRFs needs to be achieved so that the force transferred to other elements is not excessive. The parameters having a significant influence on this ratio were identified as the ratio of external diameter to fuse diameter and the thickness of the unbonded layer and its shape at the transition zone.

Sensitivity Analysis of Nonlinear Behaviour of Infill-Frames under In-Plane and Out-Of-Plane Loading

This paper addresses the sensitivity of the in-plane and out-of-plane behaviour of reinforced-concrete (RC) frames with masonry infill panels to a select number of material related parameters. Instead of general conclusions, the intention is to facilitate a deeper insight into the behaviour of infill-frames at a micro level over a wide range of drift values. A script, which has recently been developed, is used to generate the finite element (FE) models of an infill-frame with desired geometric and mechanical properties. Also, the same three-dimensional FE model is used for both in-plane and out-of-plane analyses of infill-frames. The sensitivity analyses are conducted in three sequential parts: the analyses of a masonry bare wall under one-way bending, the analyses of an infill-frame under out-of-plane loading and the sensitivity analyses of an infill-frame under in-plane loading. A simple method is delineated to overcome convergence issues which are related to the highly nonlinear finite element models to be solved using the Newton-Raphson algorithm.

Support Settlement and Slabs Reinforced with Low-Ductility Steel

The results of an investigation into the effects of relative support settlement on continuous one-way reinforced concrete slabs constructed with low-ductility mesh steel are presented herein. An experimental program has been carried out in which two full-scale continuous slabs have been subjected to an imposed relative support settlement and then loaded to failure. The behavior has been carefully monitored over the full range of loading. Photogrammetry techniques have been used to measure the displacements; this has been supplemented by the use of displacement transducers and strain gauges at key locations. It was observed that, despite the imposed settlement, the test slabs managed to surpass their ultimate design loads. The failure in each slab was brittle due to fracture of the tensile steel at the sections adjacent to the central support. A theoretical model has been developed and the results from this are compared with the experimental data.

The Effect of Consecutive Earthquakes on a Composite Structure Utilising RBRFs

Low-damage technologies have been developed in recent years which limit the damage imposed on structural elements when a building is subjected to a very rare earthquake event. This has been achieved by a capacity design approach applied to the connections in which the ductile part of the connections yields and all other structural elements remain elastic. Examples of low-damage connections are the sliding hinge joint in steel buildings and variations associated with this, and a combination of a post-tensioning system and mild steel dissipater in precast concrete and timber buildings. A system developed by the authors uses replaceable buckling restrained fuses (RBRFs) that do not require a post-tensioning system to be used conjointly. This system has been studied both experimentally and numerically. This paper considers the use of RBRFs as an energy dissipation device installed at beam-column connections in composite moment-resistant frames. These RBRFs could be replaced after a major event, and hence would cause little disruption. A 2D building frame has been modelled for a case study and its behaviour under 100-year, 500-year and 2500-year return period earthquake events has been summarised. A consecutive earthquake with a return period of 500 years or 2500 years has been applied to the building following both 500-year and 2500-year return period earthquake events. This study was performed since there is a possibility that the consecutive earthquake would occur prior to the replacement of the RBRFs. The results show that the building could still sustain the consecutive earthquakes with little additional residual displacement.